Forming is a process of configuring a part, such as a sheet, through mechanical deformation. During forming, the part is reshaped without adding or removing material. Forming is believed to follow the plastic deformation principle, where the physical shape of a part is permanently deformed. Die forming is a popular technique, in which a sheet is compressed between female and male dies having matching shapes. Other known forming techniques include rubber pad forming, hydroforming, fluid forming, blow forming, and multi-point contact forming. However, these forming techniques have drawbacks limiting their applications. For example, the die forming technique requires precision dies, which are expensive to fabricate and, accordingly, may not be feasible for small runs and/or large parts.
Incremental sheet forming is a flexible process that allows forming, from a blank sheet, parts having many different shapes without extensive preparation and sometimes without part-specific tools. The shape of a part formed using this technique depends on the path of a stylus. For any given shape, many different paths can be employed, each producing different results in the final part, such as different thickness profiles. Many failure modes are possible, such as buckling and tearing of the sheet during forming. Developing a correct forming path is essential to achieve desired parameters, such as a minimum wall thickness.
One characteristic of the forming path in the incremental sheet forming process is the orientation of the formed part relative to the plane of the blank sheet and/or relative to the direction of the stylus. Typically, the plane of the blank sheet is normal to the direction of the stylus and either the plane or the direction of the stylus may be used as a reference. The above-mentioned orientation of the formed part effects how much each portion of the blank sheet is thinned and can be controlled to achieve various thinning criteria, while avoiding the above-referenced failure modes. Conventionally, the orientation of a part is chosen manually by an operator wishing to form the part. The operator draws upon his or her past experience to help guide this orientation process. In some cases, such as for simple symmetrical shapes, the orientation of the formed part may be apparent. However, complex shapes may need to be formed in rather unusual orientations to ensure adequate thicknesses in all portions of the formed part, and these orientations cannot be manually determined with sufficient precision. As a result, complex shapes are frequently formed in suboptimal orientations, resulting in undesirable thickness profiles.